Electric lamp base



July 18, 1961 R'w. MOUAT 2,993,192

ELECTRIC LAMP-BASE Filed July 16. 1959 7 lnverw tow:

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Filed July 16, 1959, Ser. No. 827,567 2 Claims. (Cl. 339-146) Thepresent invention relates to electric lamp bases of the type comprisinga metal shell contact, a center contact in the form of a metal eyeletand a molded insulator in the form of a web uniting the shell and thecenter contact at one end of the base.

Bases of this type have been used commercially for more than fifty yearsfor incandescent lamps and are disclosed and claimed in U.S. Patent774,404 to Alfred Swan, patented November 8, 1904, and assigned to theassignee of the present application.

Cup-shaped bases having cylindrical shells provided with screw threadsand formed with a dome at one end of the shell to which end the centercontact is united by the molded insulator are also disclosed and claimedin the aforesaid patent and are in extensive use at present forincandescent lamps of the usual household sizes and wattages. Such basesare open at one end to receive the neck of the lamp bulb.

The bases are secured to the vitreous bulb of the lamp by basing cementbonding the shell to the neck of the bulb. The bulb neck is constrictedand generally cylindrical extension of the spherical part of the bulband the outer sealed end thereof of reduced diameter is enclosed by thebase in the completed lamp. In the manufacture of the lamp, the baseshell is lined with basing cement in the form of a ring applied closeenough to the rim or edge of the open end of the base shell to engagethe bulb neck and the base shell when the base is properly positioned onthe bulb with the sealed end of the neck of the bulb enclosed by thebase and the rim or edge of the open end of the base seated against ashoulder formed in the neck of the bulb at the sealed outer end of theneck.

In the present commercial form of such bases for lamps of commonhousehold sizes, such as 60 and 100 Watt lamps, the screw threads in thecylindrical wall of the shell extend from the dome toward the oppositeopen end of the shell but terminate short of the rim at the open end ofthe shell. The cylindrical wall of the shell between the rim and thethreaded portion is straight sided and constitutes the skirt of theshell. The rim is flared outwardly to seat against the shoulder on thecylindrical neck of the bulb. The rim seats on this bulb part when thebase is properly mounted on the lamp bulb.

In the manufacture of the lamp bases and of the lamps provided with suchbases by mass production methods, bulk handling, that is, packing in aloosely commingled haphazard arrangement, of the base shells, the eyeletcontacts, as well as the completed bases is highly desirable forreducing the cost of packing and handling such lamp components duringthe manufacture of the based lamps. Bulk handling of the completed basesafter the cement has been applied thereto and before the cement-linedbases have been mounted on the lamp bulb has not been practiced untilrecently and even at the present time is not entirely satisfactory.

For many years the cement-lined bases were placed by hand on trays onwhich they were separated from each other for transportation from themachine which lined with soft cement the shells of the completed basesto the machine which mounted the cement-lined bases on the lamp bulbs.This manual handling of the individual cement-lined bases was madenecessary by the location atent O Y with the cement lining of anotherbase.

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of the cement on the base. As described in the U.S. Patent 1,306,643 toSwan, patented June 10, 1919, and assigned to the assignee of thisapplication, the cement was disposed by the patented machine in the formof an annular layer or ring on the inner edge or skirt portion of thebase shell. Attempts to bulk handle bases lined with cement in thismanner resulted in smearing of the cement on the bases due to one basecoming into contact The parts of such bases most likely to be smearedwith cement when bulk handled are the exposed parts of the centercontact, the insulator and the domed part of the shell contact as theseparts of one base would enter the cement-lined opening of another baseand thus be smeared with the soft cement.

More recently, the bases have been deep-filled with the soft cement bythe apparatus disclosed and claimed in the Us. Patent 2,798,455, Beck,patented July 9, 1957, and assigned to the assignee of this application.This deepfilling of the bases has made possible bulk handling of thebases after being lined with the soft cement. In such deep-filled basesthe ring of basing cement is located a substantial distance inwardlyfrom the rim or edge of the base shell at the open end of the base toleave the skirt of the shell free from cement. However, the depth atwhich the ring of cement may be applied within the shell is limitedbecause the cement must completely fill the cross section of the annularspace between the bulb neck and the base shell for a substantialdistance longitudinally of these lamp parts to firmly bond the base andthe bulb together.

It has been found that at the depth required for obtaining a bond of therequisite strength between the base and the bulb the ring of basingcement is close enough to the rim or edge of the base shell that theexposed parts of the center contact of one base may be smeared withcement from another base when the bases are bulk handled. This happenswith sufiicient frequency to add appreciably to the cost of manufactureof the lamps due to the necessity for inspection of all the bases priorto mounting them on the lamp bulb, or all the based lamps if such basesare not inspected before being mounted on the lamp bulb, to detect anddiscard or repair those with smeared center contacts. Basing cement onthe center contacts interferes with the soldering of the lead wire tothe contact in the manufacture of the lamp. Lamps having center contactson their bases smeared with basing cement are not commerciallyacceptable because the cement is not only unsi-ghtly but, due to itselectrical insulating properties, also may act to prevent effectiveelectrical engagement between the center contact of the base and thecorresponding contact of a socket in which the lamp is mounted.

Deep filling of the bases as described above has practically eliminatedthe smearing with cement of the dome and the insulator on the bases whenbulk handled but has not completely eliminated the smearing of thecenter contacts of bulk handled cement-lined bases.

The principal object of the present invention is to provide a base ofthe above type which may be lined with cement at a depth effective forestablishing a strong bond between the base and the lamp bulb and whichcompletely eliminates the smearing of any part of bases lined with softbasing cement and bulk handled prior to being mounted on a lamp bulb.Further objects and advantages of the invention will appear from theaccompanying drawing, the following detailed description of a species ofbase embodying the invention and from the appended claims.

The invention attains its objects by forming, as by rolling, in theskirt or edge portion of the base shell an inwardly extending, outwardlyopening circumferential groove located between the flared out rim of theshell and the threaded part of the shell wall. The inward side of thegroove protrudes into the space defined by the skirt and serves as astop to limit the distance the center contact bearing end of one basecan enter the open end of another base in any relative positions of thebases and particularly when the bases are canted with respect to eachother. The inward side of the groove also serves as a dam or boundaryfor the basing cement which lines the inner surface of the shell on theside of the groove away from the rim or edge of the shell. The inwardside of the groove extends radially inward from the cylindrical wall ofthe shell a greater distance than the ocment bordering the groove andthus holds the center contact of one base out of the cement of anotherbase in any canted relative positions of bulk handled bases to keep thecenter contacts of all of such bases free from cement and thus toeliminate the need for inspection of the cement-lined bases after bulkhandling.

In the drawing:

FIG. 1 is a fragmentary side view partly in section of the bulb neckportion of an electric incandescent lamp provided with a cup-shaped baseembodying the invention, and

FIG. 2 is an enlarged, side elevational view of bases of the type shownin FIG. 1, one of said bases being shown in full and the other beingshown partly in section.

Referring to the drawing, the incandescent lamp shown in FIG. 1comprises a bulb 1 having a filament (not shown) sealed therein and abasal attached to the neck 3 of the bulb by basing cement 4. The exhausttip of the lamp is shown at 3'. The base consists of a threaded metalshell 5 of aluminum, a molded insulator 6 of glass and a bottom brasscontact 7 which is in the form of the usual eyelet united with the shell'5 by the molded insulator. The shell 5 has a re-entrant flange 8 at thedomed end thereof which acts as a collar on the insulator and holds theinsulator therein as disclosed and claimed in the co-pending applicationSerial No. 692,214, filed October 24, 1957, Rudler et al. whichapplication is assigned to the assignee of the present application.

One end of the lamp filament is connected to the base shell by theinlead wire 9 which is bent back over the end of the bulb neck andsoldered or welded as shown at 10 to the outer edge portion of the shell5. The other end of the lamp filament is connected to the inlead wire 11which extends through the funnel-shaped opening in the insulator 6 andis secured by a drop of solder 12 to the eyelet contact 7, as shown inFIG. 1.

In accordance with the present invention the skirt 13 of the base shell5 between the rim 14 and the screw threads rolled into the cylindricalWall of the shell 5 is provided with an inwardly extending, outwardlyopening circumferential groove 15. As shown in FIG. 2 when the bases 2are bul k handled, the groove 15 prevents the end contact of one basefrom engaging the ring 4 of basing cement of another base in anyrelative positions of the bases including the position shown in FIG. 2.The relative positions of the bases shown in FIG. 2 is that which wouldresult in the cement 4 smearing the exposed surface of the eyeletcontact 7 except for the provision of the circumferential groove 15. Inother relative positions assumed by the bases when bulk handled, thecement 14 is recessed within the base a sufficient distance to preventsmearing of any part of one base with cement from another base.

The basing cement is applied in the form of a ring 4 to the innersurface of the shell of each base on the side of the groove away fromthe rim 14 of the base shell 5. The apparatus disclosed and claimed inthe abovementioned U.S. Patent 2,798,455 may be used for applying thebasing cement to the base shell in this location on the shell.

' one base with cement from another base.

As presently manufactured, screw threaded aluminum bases forincandescent lamps of 60 and watt sizes for operation on power sourcesof commercial voltages are approximately fifteen-sixteenths of an inchin overall length and have an outside diameter of 1.050 to 1.075 inchesat the flared-out rim 14 of the base shell. The outside diameter of theshell at the skirt 13 is approximately one inch and the eyelet contact 7has a diameter of approximately seven-sixteenths of an inch. The depthof the base from the part of maximum diameter of the dome to the outersurface of the eyelet contact 7 is approximately five-eights of an inchand the dome has a radius of curvature of approximatelyfive-thirty-seconds of an inch and a depth of approximatelythree-sixteenths of an inch. 1

The thread is rolled in the cylindrical wall of the shell at seven turnsto the inch. The diameter of the thread is 1.029 to 1.037 inches at itscrest and 0.965 to 0.971 of an inch at its root and, in section, is inthe form of reversed arcs each having a radius of 0.047 of an inch withno taper, The thread terminates at the domedshaped end of the shell andextends axially of the shell to within about one-eighth of an inch ofthe rim 14.

The objects of this invention are attained with bases of thisstructurewhen the circumferential groove 15, formed by rolling, forexample, has a width of approximately 0.050 of an inch, measured asshown at A in FIG. 2, is located approximately 0.100 of an inch inwardfrom the rim 14 of the shell, measured as shown at B in this figure, andhas a depth such that the inner diameter of the shell at the groove isapproximately 0.965 of an inch. The inner diameter of the shell at thecylindrical skirt portion 13 bordering the sides of the groove isapproxiamtely 0.990 of an inch so that the groove, in effect,constitutes a ledge projecting or protruding inward from the cylindricalsurface of the skirt portion 13 of the shell 5 and serves to prevent theeyelet contact 7 of one base coming into engagement with and beingsmeared by the cement 4 of another base when the bases are bulk handled.

The basing cement is applied as shown in FIG. 2 so as to border on theside of the groove 15 away from the rim 14 ofthe shell and is in theform of a slightly flattened ring with the part thereof bordering thegroove 15 spaced approximately 0.150 of an inch from the rim 14. Whenthe basing cement is cured by heating after the cement lined base isplaced on the neck of the lamp bulb it swells while being cured andfills the annular space between the base shell and the part of the neckenclosed by the shell, including the space surrounded by the groovedskirt portion of the base shell, as shown in FIG. 1.

As pointed out above, bases of the above structure may be bulk handledafter the basing cement has been applied thereto and before the base iscemented to the cylindrical neck 3 of the lamp bulb 1 without smearingFurther, the strength of the bond between the bulb neck 3 and the base 2cemented thereto is sufficient for commercial acceptance of the basedlamp. The torque strength of the bond is, of course, enhanced by theincreased area and the irregular surface of the shell 5 at the groovedskirt portion, the groove 15 being embedded in the cement 4 after thecement has been cured and when the base 2 is properly mountedon the lampbulb neck 3 with the rim 14 seated against the shoulder 16 on the bulbneck 3 as shown in FIG. 1.

A further advantage secured by providing a groove 15 in the skirt 13 ofthe base shell as described above, is

obtained when the base shells are bulk handled before the insulator 6and the eyelet contact 7 is united therewith and when the completedbases are bulk handled. At each of these steps in the manufacture of thebase difficulty has been encountered heretofore in the bulk handledshells or bases sticking together. This has necessitated manualseparation of such base shells in order to feed such shells to basemaking machines by automatic means, during the dipping of the completedbases for brightening purposes, while feeding the completed bases to thecement applying machine and while feeding the cement lined bases to thelamp basing machine. The groove 15 also strengthens the base shells tobetter withstand such bulk handling.

Thus, the present invention has eliminated completely individual manualhandling and made practical the bulk handling of the base shells and thecompleted bases at any stage of the manufacture of a lamp having suchbases cemented thereto with consequent substantial savings in themanufacturing cost of lamps equipped with bases of the kind describedabove while completely eliminating smearing of the bases and increasingthe strength of the bond between base and the lamp bulb.

While the invention has been described in connection with bases of aparticular size having aluminum base shells, it will be understood thatthe above description is for the purpose of giving an example of theinvention and that the invention is useful in connection with differentsizes of screw-threaded bases of similar shape with shell contacts madeof brass or aluminum and with insulators of other shapes and material,such as thermo-setting organic plastic material.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A cup-shaped base for attachment by basing cement to the cylindricalneck of a lamp bulb comprising a generally cylindrical screw threadedshell contact domeshaped at one end and having a cylindrical skirt atthe opposite end thereof, a center eyelet contact and a molded web ofelectrically insulating material uniting said shell contact and saideyelet contact at the domed end of said shell contact with the eyeletcontact exposed at the end of the base, said shell contact having aflared rim for seating the base on a bulb neck and an inwardly extendingoutwardly opening circumferential groove in the skirt of the shell and aring of basing cement on the inner surface of the shell contact on theside of the groove away from the flared rim and bordering the groove,the said groove extending radially inward of the shell a sufiicientdistance to protect the basing cement from casual contacts with theeyelet contacts of similar bases when bulk handled.

i2. A cup-shaped base for attachment by basing cement to the cylindricalneck of a lamp bulb comprising a generally cylindrical screw threadedshell contact domeshaped at one end and having a cylindrical skirt atthe opposite end thereof, a center eyelet contact and a molded web ofelectrically insulating material uniting said shell contact and saideyelet contact at the domed end of said shell contact with the eyeletcontact exposed at the end of the base, said shell contact having aflared rim for seating the base on a bulb neck, said skirt having acircumferential protrusion extending into the space defined thereby anda ring of basing cement on the inner surface of the shell contact on theside of the protrusion away from the flared rim, the circumferentialprotrusion extending into the space defined by the shell a suflicientdistance to protect the basing cement from casual contacts with theeyelet contacts of similar bases when bulk handled.

References Cited in the file of this patent UNITED STATES PATENTS430,437 Rockwell June 17, 1890 2,733,419 Beck Jan. 371, 1956 2,798,455Beck July 9, 1957

